In appendiceal cancers, GNAS mutations are reported with high frequency in low- and high-grade appendiceal mucinous neoplasms [15,16,30,33], in codons 601 (c.601 C>T, p. Arg201His) and 602 (c.602 G>A, p. Arg201Cys), in which they often occur together with mutations in the KRAS gene as early as G1 and G2 [15] stages and are associated with abundant mucin production, without affecting patient survival [27], and in mucinous adenocarcinomas of the appendix. Here, GNAS is linked to mucinous adenocarcinoma of the appendix.